Photomodification of sensitizers commonly used in photosensitized tumour therapy

摘要

Photostability studies of porphyrin-type sensitizers performed in aqueous solutions, model systems (sensitizers bound to human serum albumin or in a suspension of released erythrocyte ghosts) and in tumour tissue reveal that similar photomodification takes place in all investigated environments: photobleaching during exposure to light is followed by the formation of red-absorbing photoproducts. Photoproducts are not formed in the solutions of the less photostable sensitizer chlorin e_6 and the most photostable sensitizer aluminium phthalocyanine tetrasulphonate. Interaction with photooxidizible biomolecules increases the photobleaching rate of porphyrin-type sensitizers. This should be taken into account in the estimation of optimal photodynamic doses. The modified formula including photodestruction of sensitizer and formation of photoproduct is suggested.